\input{preamble-standalone.ltx} \begin{document} % Ex. No. 141 (Section 21.2.2 : More complex example of a line-circle intersection) \begin{tikzpicture}[scale=.75] \tkzDefPoint(0,0){A} \tkzDefPoint(8,0){B} \tkzDefMidPoint(A,B) \tkzGetPoint{O} \tkzDrawCircle(O,B) \tkzDefMidPoint(O,B) \tkzGetPoint{O'} \tkzDrawCircle(O',B) \tkzDefTangent[from=A](O',B) \tkzGetSecondPoint{E} \tkzInterLC(A,E)(O,B) \tkzGetSecondPoint{D} \tkzDefPointBy[projection=onto A--B](D) \tkzGetPoint{F} \tkzMarkRightAngle(D,F,B) \tkzDrawSegments(A,D A,B D,F) \tkzDrawSegments[color=red,line width=1pt, opacity=.4](A,O F,B) \tkzDrawPoints(A,B,O,O',E,D) \tkzLabelPoints(A,B,O,O',E,D) \end{tikzpicture} \end{document}